For the full versions of these articles see bmj.com CLINICAL REVIEW

Cauda equina syndrome

Chris Lavy, Andrew James, James Wilson-MacDonald, Jeremy Fairbank

Nuffield Department of An understanding of cauda equina syndrome is impor- intervertebral disc herniation of 1.8 per million Orthopaedic Surgery, Nuffield tant not only to orthopaedic surgeons and neurosur- population.3 Using US data on annual incidence of Orthopaedic Centre, Oxford geons but also to general practitioners, emergency symptomatic disc herniation (1500 per million popula- OX3 7LD Correspondence to: C Lavy department staff, and other specialists to whom these tion), the author estimates that each year 0.12% of her- [email protected] patients present. Recognition of the syndrome by all niated discs are likely to cause cauda equina syndrome. groups of clinicians is often delayed as it presents with We suspect this is an underestimate and are conducting Cite this as: BMJ 2009;338:b936 bladder, bowel, and sexual problems, which are com- our own review in the United Kingdom, but if these fig- doi:10.1136/bmj.b936 mon complaints and have a variety of causes. Patients ures are even approximately correct then most UK gen- may not mention such symptoms because of embarrass- eral practitioners are unlikely to see even one true case ment or because the onset is slow and insidious. caused by intervertebral disc herniation in their career. Cauda equina syndrome is a clinical area that attracts a high risk of litigation. Although symptoms have poor How does cauda equina syndrome present and what predictive value on their own for the syndrome, it is symptoms suggest it? important to document the nature and timing of blad- A history of perianal sensory loss and sphincter distur- der, bowel, and sexual symptoms (along with any asso- bance, with or without urinary retention, suggests the ciated clinical findings), particularly if they are new, presence of cauda equina syndrome (figure 1 illustrates especially in those with a history of back pain and asso- the anatomy of the lower lumbar and sacral spine ciated leg pain, and to make a timely referral for appro- showing the cauda equina). Three classic patterns of priate investigation and expert treatment. presentation have been described. 4 It can present This review aims to highlight cauda equina syn- acutely as the first symptom of lumbar disc herniation drome as a possible clinical diagnosis, review the evi- (type 1); as the endpoint of a long history of chronic dence for an emergency surgical approach, and back pain with or without sciatica (type 2); or insi- maintain an awareness of the medicolegal issues that diously in a more chronic way with slow progression surround the condition. to numbness and urinary symptoms (type 3). Most clin- icians now divide cauda equina syndrome into two What is cauda equina syndrome and how common is it? clinical categories 4: cauda equina syndrome with Cauda equina syndrome results from the dysfunction retention, in which there is established urinary reten- of multiple sacral and lumbar nerve roots in the lumbar tion; and incomplete cauda equina syndrome, in which vertebral canal. Such root dysfunction can cause a there is reduced urinary sensation, loss of desire to combination of clinical features, but the term cauda void, or a poor stream, but no established retention or equina syndrome is used only when these include overflow. 5 Often the slower the presentation, the better impairment of bladder, bowel, or sexual function, tolerated the symptoms are and the less likely the and perianal or “saddle” numbness.12 (box) patient is to be alarmed. Patients with pre-existing A retrospective review in Slovenia found an annual bladder and incontinence problems resulting from incidence of cauda equina syndrome resulting from other disease may also present late.

What causes cauda equina syndrome? Clinical diagnosis of cauda equina syndrome The commonest cause of cauda equina syndrome in  Dysfunction of bladder, bowel, or sexual function our practice and the focal causative condition in the SOURCES AND 6 SELECTION CRITERIA  Sensory changes in saddle or perianal area literature is compression arising from large central lumbar disc herniation at the L4/5 and L5/S1 level. Other possible symptoms We searched Medline Parke and colleagues suggest that there is an area of  using the search term Back pain (with or without sciatic-type pains) relative hypovascularity at the proximal portion of “cauda equina  Sensory changes or numbness in the lower limbs the cauda equina.7 Blood supply alterations resulting syndrome”.Inaddition,  Lower limb weakness from nerve root pressure may therefore be of greater we used our personal  importance in this region of the cauda equina than else- reference archives and Reduction or loss of reflexes in the lower limbs consulted other experts.  Unilateral or bilateral symptoms where, with rapid changes allowing less adaptation than those of a slower onset.

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Patients may be predisposed to cauda equina syn- TIPS FOR drome if they have a congenitally narrow spinal canal NON-SPECIALISTS or have acquired spinal stenosis arising from a combi- Spinal cord  Be alert to the nation of degenerative changes of the disc and the seg- development of new mental posterior joints with consequent thickening of Conus medullaris symptoms of perianal the ligamentum flavum and narrowing of the available sensory change or canal cross section. bladder symptoms in Numerousotherlesscommoncausesofcaudaequina patients with an Cauda equina syndromehavebeenreported—for example, spinal increase in back pain injury with fractures or subluxation. Spinal neoplasms or sciatica of metastatic or primary origin can cause compression,  Be aware that cauda usually accompanied by marked pain and often as part equina syndrome can of a chronic condition. Infective causes with abscess for- arise insidiously mation or bony involvement, either within the spinal when patients who canal or impinging on it, may also cause cauda equina Filium terminale have had back and syndrome.8 The spine is the most commonly affected leg pain for a long skeletal site for tuberculosis, and Pott’s paralysis is well time develop bladder Sciatic nerve documented.9 A wide range of iatrogenic causes are symptoms gradually reported, including manipulation,10 spinal  Establish the most anaesthesia,11 postoperative complications such as appropriate channel 12 Fig 1 | Anatomy of the lower lumbar and sacral spine showing haematoma or gelfoam implanted to protect the dura. the cauda equina for referral or further Other space-occupying lesions, such as nerve derived investigation in tumours, schwannomas, ependymomas, facet joint suspected cases in cysts,13 perineural Tarlov cysts, haemangiomas,14 vena your specialty imaging (MRI) is the imaging modality of choice. It does varix,15 and hydatid cysts16 are also recognised.  not define bone as clearly as computed tomography Make sure that (CT)butisbetteratshowingsofttissuessuchasinter- clinical What features on examination suggest cauda equina vertebral disc, ligamentum flavum, dural sac, and documentation is syndrome? nerve roots. In resource poor settings where neither clear and well When cauda equina syndrome is suspected a neurologi- MRI nor CT is available myelography can be useful in recorded cal examination of the legs should be performed, includ- showing the presence and site of compression of the ing perianal sensation and an assessment of anal tone cauda equina.19 Figures 2 and 3 show examples of (table). This is easily done in the lateral position: perineal cauda equina on MRI scans. sensation can be tested from the outside in towards the sphincter using a gentle gloved finger stroke and, if there How is cauda equina syndrome treated? is any uncertainty, a folded tissue and an unfolded paper When a patient has clinical features of cauda equina syn- clip. After this, a rectal examination can be performed. drome and an MRI scan shows a potentially reversible Loss or diminution of the bulbocavernosus reflex cause of pressure on the cauda equina then current con- (whereby stimulation of the glans, penis, or clitoris sensus recommends surgical decompression.6 This arti- causes reflex contraction of the anal sphincter) is sugges- cle will not review management of all the conditions tiveofcaudaequinasyndromeasthereflexismediated leading to cauda equina syndrome, and some causes through the sacral roots. such as tumour clearly require detailed assessment of the nature and extent of the pathology. However, most How should suspected cauda equina syndrome be cases of cauda equina syndrome are caused by hernia- investigated? tion of the lumbar disc, for which the surgery indicated is Recently published guidelines for the management of patients with back pain and neurological signs recom- mend urgent surgical referral for suspected cauda equina syndrome.17 Clinical diagnosis of cauda equina syn- drome even by resident neurosurgeons has a 43% false positive rate,18 so accurate confirmatory imaging is important. In the United Kingdom magnetic resonance

Motor sensory and reflex components of lumbar and sacral roots

Nerve level Motor innervation Sensory innervation Reflexes L2 Hip flexors, thigh adductors Upper thigh L3 Quadriceps, knee extensors Anterolateral thigh L4 Knee extensors and foot dorsiflexors Anteromedial calf Patella, knee L5 Foot and toe dorsiflexors (extensor hallucis Lateral calf, dorsum of foot Fig 2 | Left: MRI scan showing compression of the cauda longus) equina (arrow) due to a large posterior disc herniation at S1,2 Foot and toe plantar flexors Lateral side of foot, sole of foot Ankle L4/5. Right: MRI scan showing a large disc herniation at S2, S3, S4, S5 Sphincters Perianal and saddle Bulbocaverno- L5/S1 (arrow) bulging posteriorly and compressing the cauda sus equina

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QUESTIONS FOR FUTURE RESEARCH  Multicentre outcome studies are needed to define which subgroups of cauda equina syndrome may benefit from emergency surgery and which do not need such urgent treatment  Such studies may also develop prognostic indicators such as the length and degree of compression of the cauda equina  Qualitative research is needed to determine appropriate questions and appropriate language to inquire about sensation in intimate areas

decompression at the level of the herniation, usually involving discectomy. The operation can be very demanding technically, and great care is needed to avoid causing further damage to nerve roots or tearing tightly compressed dura.

Is surgery for cauda equina syndrome urgent? The urgency of surgery remains controversial. When there is pressure on the cauda equina causing loss of sphincter control it would be understandable to think that the ideal treatment would be to remove the pres- sure as soon as possible with surgery. Ethical consid- erations will not allow this hypothesis to be tested by a randomised study, and it is very difficult to prove by literature review of retrospective and cohort studies (level 3 evidence) for two reasons. Firstly, the time of onset of symptoms is difficult to specify. Thus it is dif- Fig 3 | Top: Axial cross sectional MRI view at the level of L5/S1 of a patient with cauda equina syndrome showing a large ficult to define the delay between symptoms and sur- irregular disc herniation (arrow) occupying most of the gery. Secondly, any discussion is muddied by many vertebral canal. Bottom: By contrast, a cross sectional MRI published (mainly retrospective) series containing a view at L5/S1 in a patient without cauda equina syndrome mix of patients with both incomplete cauda equina syn- showing an unobstructed vertebral canal (arrows from top drome and cauda equina syndrome with retention. down: body of S1 vertebra; vertebral canal containing cauda The authors of two recent reviews20 21 argue that only equina with no compression; spine of S1) incomplete cauda equina syndrome requires emergency surgery to try to stem the deterioration in bladder func- surgery. Incontinence at presentation is a poor prog- 23 tion. They conclude that in patients with cauda equina nostic feature in the largest prospective series. syndrome with retention the clinical outcome is poor A review that is widely quoted suggests that inter- anyway and bears no relation to timing of surgery. vention less than 48 hours after the onset of symptoms will produce a better outcome than intervention Thus these patients can wait until an elective surgical 6 list the next morning rather than having a potentially delayed for longer than this. These data have been selectively reanalysed24 and suggest that the outcome difficult operation in the middle of the night, when cir- for both types of cauda equina syndrome (with reten- cumstances are less than optimal. tion, or incomplete) is better with interventions within 22 23 Two other recently published UK series have rather than after 24 hours. In a further analysis of the found that outcome is independent of the timing of selected retrospective series, the authors noted that of 47 patients having surgery within 24 hours, 41 (87%) recovered normal bladder function, whereas of 46 APATIENT’S PERSPECTIVE patients having surgery later than 24 hours, only 20 Iwasn’tthatconcernedatfirst.Ihadjustsneezed.Ihadn’t even lifted anything heavy. The (43%) recovered normal bladder function.25 sudden, searing lower back pain was unpleasantly familiar to me and it usually got better by A recent meta-analysis supports the view that early itself. I didn’t notice anything unusual until I started to get pins and needles in both my feet. surgery is related to better results with incomplete And then, after painfully struggling to the toilet, I remember wiping myself with the toilet cauda equina syndrome, but the case for cauda equina paper and it feeling decidedly odd—not completely numb but distant. It was my refusal to syndrome with retention is less certain.4 We urge the admit to numbness that fooled my general practitioner. He asked if I could feel him touching establishment of a multicentre outcome study with me, not whether his touch felt normal. He organised an urgent outpatient referral for three clear clinical entry points and clear separation of days later. Foolishly I just waited, not reporting the progressive loss of sensation, muscle incomplete cases and those with retention. fasciculation, creeping incontinence, and onset of a deep burning pain around my perineum. Unable to arrange ambulance transfer, a friend took me to the hospital lying in the back of What are the medicolegal implications of cauda equina his estate car. Within 90 minutes of arrival I had had an MRI scan and was in theatre syndrome? undergoing an L4/5 discectomy. Two days later, the postoperative anxiety was replaced by euphoria when I managed to stand unaided and pass urine into a bottle. Persisting cauda equina syndrome has a devastating effect on personal and social life, and its

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SUMMARY POINTS patients with spinal disorders need to be aware of cauda equina syndrome and its possible complications. Cauda equina syndrome is rare, but devastating if symptoms persist We acknowledge the help of our departmental colleagues in preparing this Clinical diagnosis is not easy and even in experienced hands is associated with a 43% false clinical review, in particular James Teh, Gavin Bowden, Nas Qureshi, Adi positive rate Zubovitch, David McKenna, David Mant, Elaine Buchanan, and Louise Hailey. Contributors: This article was suggested after discussion at a The investigation of choice is magnetic resonance imaging departmental audit meeting. All authors contributed to the research and Once urinary retention has occurred the prognosis is worse writing. CL is the guarantor. Competing interests: None declared. Good retrospective evidence supports urgent surgery especially in early cases Provenance and peer review: Not commissioned; externally peer Litigation is common when the patient has residual symptoms reviewed. Patient consent obtained.

1 Kostuik JP. Medicolegal consequences of cauda equina syndrome: mismanagement is one of the commonest causes for an overview. Neurosurg Focus 2004;16(6):e8. litigation in spinal surgery. Most patients are young 2 Kostuik JP, Harrington I, Alexander D, Rand W, Evans D. Cauda equina to middle aged and in work before they develop syndrome and lumbar disc herniation. J Bone Joint Surg Am 1986;68:386-91. cauda equina syndrome, so the size of claims is large. 3 Podnar S. Epidemiology of cauda equina and conus medullaris The presence of residual symptoms means that many lesions. Muscle Nerve 2007;35:529-31. of these patients are unable to work and have genito- 4 DeLong WB, Polissar N, Neradilek B. Timing of surgery in cauda equina syndrome with urinary retention: meta-analysis of urinary and bowel symptoms. From 1997 to 2006 the observational studies. J Neurosurg Spine 2008;8:305-20. NHS Litigation Authority dealt with 107 cases in Eng- 5 Gleave JR, Macfarlane R. Cauda equina syndrome: what is the land in which care in hospital had been compromised relationship between timing of surgery and outcome? Br J Neurosurg 2002;16:325-8. (NHS Litigation Authority, personal communication, 6 Ahn UM, Ahn NU, Buchowski JM, Garrett ES, Sieber AN, Kostuik JP. 3 2008). Extrapolating from previous data, we would Cauda equina syndrome secondary to lumbar disc herniation: a expect about 100 new cases of cauda equina syndrome meta-analysis of surgical outcomes. Spine 2000;25:1515-22. 7 Parke WW, Gammell K, Rothman RH. Arterial vascularization of the annually in England, suggesting that at least 10% of cauda equina. J Bone Joint Surg Am 1981;63:53-62. cases involve litigation. The NHS Litigation Authority 8 Cohen DB. Infectious origins of cauda equina syndrome. Neurosurg reported that between 1997 and 2006 in 35% of litiga- Focus 2004;16(6):e2. tion cases the primary complaint was against the emer- 9 Nigam V, Chhabra HS. Easy drainage of presacral abscess. Eur Spine J 2007;16(suppl 3):322-5. gency department and in 52% it was against the 10 Haldeman S, Rubinstein SM. Cauda equina syndrome in patients inpatient management team (personal communication undergoing manipulation of the lumbar spine. Spine as above). In the remaining cases the primary com- 1992;17:1469-73. 11 Loo CC, Irestedt L. Cauda equina syndrome after spinal anaesthesia plaints were against other clinical areas, such as out- with hyperbaric 5% lignocaine: a review of six cases of cauda equina patients. The responsible clinician in the litigation syndrome reported to the Swedish Pharmaceutical Insurance 1993- cases was in orthopaedics in 52% of cases, the emer- 1997. Acta Anaesthesiol Scand 1999;43:371-9. 12 Jensen RL. Cauda equina syndrome as a postoperative complication gency department in 27%, and neurosurgery in 8%; of lumbar spine surgery. Neurosurg Focus 2004;16(6):e7. in the remaining cases the responsible clinician varied 13 Shaw M, Birch N. Facet joint cysts causing cauda equina across various specialties. compression. JSpinalDisordTech2004;17:442-5. 14 Ahn H, Jhaveri S, Yee A, Finkelstein J. Lumbar vertebral hemangioma JF and JW-MacD have prepared 22 medical negli- causing cauda equina syndrome: a case report. Spine gence reports in cases of cauda equina syndrome 2005;30:E662-4. over the past five years. The average delay to diagnosis 15 Moonis G, Hurst RW, Simon SL, Zager EL. Intradural venous varix: a rare cause of an intradural lumbar spine lesion. Spine was 67 hours and to treatment 6.14 days. These delays 2003;28:E430-2. were attributed to orthopaedic surgeons in 32% of 16 Adilay U, Tugcu B, Gunes M, Gunaldi O, Gunal M, Eseoglu M. Cauda cases, general practitioners in 18%, and others in equina syndrome caused by primary lumbosacral and pelvic hydatid cyst: a case report. Minim Invasive Neurosurg 2007;50:292-5. 14%, but in 34% of cases there was no clear case to 17 Haswell K, Gilmour J, Moore B. Clinical decision rules for answer. Fourteen per cent of patients had received identification of low back pain patients with neurologic involvement their treatment within 24 hours and 32% within 48 in primary care. Spine 2008;33:68-73. 18 Bell DA, Collie D, Statham PF. Cauda equina syndrome: what is the hours. All patients had moderate or severe bowel and correlation between clinical assessment and MRI scanning? Br J genitourinary symptoms. Most also had persisting Neurosurg 2007;21:201-3. back pain that would probably have occurred what- 19 Akbar A, Mahar A. Lumbar disc prolapse: management and outcome analysis of 96 surgically treated patients. JPakMedAssoc ever the timing of surgery. Doctors who manage 2002;52(2):62-5. 20 Gleave JR, MacFarlane R. Prognosis for recovery of bladder function following lumbar central disc prolapse. Br J Neurosurg 1990;4:205-9. ADDITIONAL EDUCATIONAL RESOURCES* 21 Gleave J, MacFarlane R. Commentary. Br J Neurosurg 2005;19:307-8.  Cauda Equina Syndrome Resource Center (www.caudaequina.org)—Support group for [Commentary on: Todd NV. Cauda equina syndrome: the timing of people with cauda equina syndrome to share information about the condition surgery probably does influence outcome. Br J Neurosurg 2005;19:301-6.]  BackPainExpert (www.backpainexpert.co.uk/CaudaEquinaSyndrome.html)—Patient 22 McCarthy MJ, Aylott CE, Grevitt MP, Hegarty J. Cauda equina information site with articles written by invited experts syndrome: factors affecting long-term functional and sphincteric  Wikipedia (http://en.wikipedia.org/wiki/Cauda_equina)—Part of the online editable outcome. Spine 2007;32:207-16. 23 Qureshi A, Sell P. Cauda equina syndrome treated by surgical encyclopedia wikipedia; anyone may post comments or make changes decompression: the influence of timing on surgical outcome. Eur  Cauda Equina (http://orthoinfo.aaos.org/topic.cfm?topic=A00362)—Information on Spine J 2007;16:2143-51. the website of the American Academy of Orthopaedic surgeons 24 Todd NV. Cauda equina syndrome: the timing of surgery probably does influence outcome. Br J Neurosurg 2005;19:301-6. *All these websites are free and do not need registration 25 Jerwood D, Todd NV. Reanalysis of the timing of cauda equina surgery. Br J Neurosurg 2006;20:178-9.

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